Building consultant vs town planner vs structural engineer. Three professionals, three questions.

Three different professionals can examine the same property and give you completely different answers. Each addresses a different question. Each has a different fee structure. Each is the right answer to a specific question at a specific moment in your buying or building journey.

This post is the comparison: when to hire which professional, what to expect for the fee, and where the lines blur.

Building consultant / building inspector

What they assess

The current physical condition of the building. Whether it is structurally sound, weatherproof, free of pest infestation, compliant with the building code at the time it was built.

Typical scope

• Roof condition (cracked tiles, leaking flashings, structural sag)
• Wall condition (cracks, rising damp, settling)
• Floor condition (level, joist health, sub-floor ventilation)
• Plumbing visible inspection (no destructive opening)
• Electrical visible inspection (no testing)
• Pest assessment (active termites, evidence of past activity, conditions conducive to future infestation)
• Identifying obvious unauthorised work or non-compliant alterations

Typical fees

• Standard residential inspection: $400-700
• Thorough inspection with cavity wall investigation: $1,200-2,500
• Strata building inspection (apartment block): $300-500
• Pest inspection (separate from building, sometimes combined): $250-400

When to use

Before exchange on any property over 5-10 years old. The cost is small. The information is invaluable. Skipping a building inspection is the single most common preventable mistake in Australian property purchase.

What they do NOT cover

• Future development potential (that is the town planner)
• Detailed structural calculations (that is the structural engineer)
• Asbestos identification (that is a specialist asbestos consultant)
• Heritage assessment (that is a heritage consultant)
• Pool safety compliance (that is a pool safety inspector)

Town planner

What they assess

The development potential of the property under the relevant planning instruments. What is permitted, what requires DA, what is prohibited, what conditions apply.

Typical scope

• Zone identification and permitted uses
• Build envelope (setbacks, height, FSR, site coverage)
• Hazard overlays (flood, bushfire, coastal, landslip)
• Heritage and character status
• Specific overlays (transport noise, biodiversity, koala habitat)
• Likely DA timeline and assessment criteria
• Realistic objections or constraints

Typical fees

• Pre-purchase consultation (60 minutes): $250-450
• Pre-purchase written advice on specific project: $800-2,500
• Full DA preparation and submission: $5,000-25,000+ depending on complexity
• Hourly rate for ongoing advice: $250-450

When to use

Before exchange when redevelopment is part of your purchase rationale. After exchange when actively planning a DA. The pre-purchase consultation is one of the highest-leverage spends in property due diligence for redevelopment-intending buyers.

What they do NOT cover

• Physical building condition (that is the building inspector)
• Structural design calculations (that is the structural engineer)
• Architectural design (that is the architect)
• Property valuation (that is the registered valuer)

Structural engineer

What they assess

The structural capacity of the existing building and the requirements for any proposed new or modified structures.

Typical scope

• Foundation design and integrity
• Load-bearing capacity of existing structure (for proposed modifications)
• Bracing and lateral load resistance
• Beam, column and slab design for new construction
• Retaining wall design
• Footing recommendations based on soil
• Certification of work to meet building code

Typical fees

• Structural feasibility study for proposed modification: $1,500-4,000
• Full structural design for a new build: $4,000-12,000 (excluded from architectural fees)
• Structural certification of completed work: $800-2,500
• Hourly rate: $180-300

When to use

When the project involves structural modifications. Removing internal walls, adding a second storey, building on a sloped site, designing foundations on poor soil, certifying compliance with structural codes.

The structural engineer is essential for:

• Substantial extensions or new builds
• Any work that affects the building's load paths
• Sites with geotechnical complexity
• Builds in cyclone or seismic zones

What they do NOT cover

• Planning approvals (that is the town planner)
• Architectural design (that is the architect)
• Existing building condition (overlap with building inspector but they look at structure not condition)
• Environmental compliance

Where the lines blur

Three boundary areas where the choice of professional matters:

Boundary 1: structural integrity of an existing building

A building inspector identifies cracks. A structural engineer assesses whether the cracks are significant.

If your building inspector flags concern about a crack, foundation movement, or sagging beam, the next call is to a structural engineer, not back to the building inspector. The engineer's $1,500 assessment tells you whether the issue is cosmetic or structural.

Boundary 2: development feasibility for a complex site

A town planner tells you the planning constraints. A structural engineer tells you the build constraints.

For a sloped lot with subsidiary considerations (riparian buffer, easements, retaining requirements), you may need both: the planner confirms planning permissibility and the engineer confirms physical buildability.

Boundary 3: pre-purchase scope of work for a renovation

A building inspector tells you the existing dwelling is in OK condition. A town planner tells you the proposed renovation is planning-permissible. A structural engineer tells you the proposed structural changes are technically feasible.

For a substantial renovation, all three may be needed. Sequence: planner first (is the project permissible?), then engineer (is it technically feasible at reasonable cost?), then building inspector (is the existing building a sound starting point?).

Common mistakes

Three patterns:

Mistake 1: hiring the wrong professional for the question

Asking a building inspector about development potential. Asking a town planner about structural safety. Asking an engineer about planning rules. Each gives you a partial answer at full hourly rate.

The fix: match the question to the professional. Use the table above.

Mistake 2: skipping the cheaper professional to "save"

A buyer who skips the $600 building inspector to "save money" sometimes discovers $30k of building defects after settlement. The saving was illusory.

The fix: spend $600 to potentially save $30k.

Mistake 3: relying on a single professional for a complex question

A 600 square metre lot in a heritage character area with a sloped block and a creek along the rear boundary cannot be assessed by any single professional. The combined input from the town planner (planning), the structural engineer (slope and creek-buffer), and the building inspector (existing dwelling) is needed.

The fix: scope the questions in advance, then engage the right professional(s) for each.

The 90-day pre-exchange plan

For a serious purchase of a redevelopment-intent property:

60-90 days before exchange

• Town planner consultation: 60 minutes, $300-500
• Confirm planning feasibility for intended project

30-60 days before exchange

• Comprehensive building and pest inspection: $1,200-2,500
• Structural engineer assessment if any concerns from building inspection: $1,500-4,000

1-7 days before exchange

• Final title search via conveyancer
• Strata report if applicable: $300-500
• Council rates and land tax search

Total pre-exchange spend on professional advice: typically $2,500-6,000 for a property where significant work is intended.

For a straightforward purchase of an existing dwelling to live in as-is, the spend can be $700-1,500 (building inspection plus standard conveyancing).

• The town planner uses the report to confirm zone, overlays, and constraints quickly
• The building inspector uses the report to understand the lot's heritage and character context
• The structural engineer uses the report to understand soil type, slope, and any specific structural considerations

The data layer compounds with professional judgment. SafeBuy's $23 cost or Pro tier subscription is not a substitute for professional advice but it makes the professional advice more focused and therefore more cost-effective.

Three professionals. Three questions. Three moments. Knowing which to hire when is one of the most under-discussed skills in Australian property buying.